The present invention is concerned with treating patients suffering from cancer by administering to the patients certain thioarabinofuranosyl compounds. Compounds employed according to the present invention have exhibited good anticancer activity. Compounds employed according to the present invention are in the beta configuration as contrasted to the alpha configuration, which failed to exhibit anticancer activity. The present invention also relates to inhibiting DNA replication in a mammalian cell by contacting with the thioarabinofuranosyl compounds. The present invention also relates to a new process for preparing the compounds employed according to the present invention.
Vast amounts of research have accrued over the years related to developing treatments against cancers to inhibit and kill tumor cells. Some of this research has resulted in achieving some success in finding clinically approved treatments. Nevertheless, efforts continue at an ever-increasing rate in view of the extreme difficulty in uncovering promising anticancer treatments. For example, even when a compound is found to have cytotoxic activity, there is no predictability of it being selective against cancer cells.
One particular compound that has been used rather widespread is cytosine arabinoside, commonly referred to as Ara-C.
It has been found according to the present invention that certain thioarabinofuranosyl cytosine compounds are suitable as anticancer agents. The presence of the thio sugar moiety surprisingly makes it possible to achieve good antitumor activity. More particularly, the present invention relates to treating a mammalian host in need of an anticancer treatment by administering to the host an effective anticancer amount of at least one compound represented by the following formula 1: 
wherein
each R individually is H or an aliphatic or aromatic acyl group;
A is selected from the group consisting of 
X is selected from the group consisting of hydrogen, fluoro, alkoxy, alkyl, haloalkyl, alkenyl, haloalkenyl, alkynyl, amino, monoalkylamino, dialkylamino, cyano and nitro.
It has also been found according to the present invention that the above-disclosed compounds of formula 1 can be used to inhibit DNA replication in a mammalian cell by contacting the cell with at least one of these compounds.
The present invention is also concerned with a process for preparing the above-identified compounds. The compounds employed according to the present invention can be prepared by:
A) reacting a 2,3,5-tri-O-aryl or alkyl-4-xylose diaryl or dialkyl dithioacetal such as 2,3,5-tri-O-benzyl-L-xylose-dibenzyl dithioacetal in the presence of a leaving group at the 4 hydroxyl to produce the corresponding 1,4-dithio-D-arabinofuranoside such as benzyl 2,3,5-tri-O-benzyl-1,4-dithio-D-arabinofuranoside;
B) subjecting the product from step A) to acidolysis to form the corresponding O-acetyl-4-thio-D arabinofuranose such as 2,3,5-tri-O-benzyl-1-O-acetyl-4-thio-D-arabinofuranose;
C) reacting the product of step B with a cytosine, a 5- or 6-aza compound or a suitably blocked derivative thereof forming a corresponding 4-thio-xcex1,xcex2-D-arabinofuranosyl) compound such as, in the case of cytosine, 1-(2,3,5-tri-O-benzyl-4-thio-xcex1,xcex2-D-arabinofuranosyl cytosine;
D) converting the compound of step C) by hydrolysis to the corresponding thio sugar derivative such as 1-(4-thio-xcex1,xcex2-D-arabinofuranosyl) cytosine;
E) separating out the xcex1 form of the anomeric mixture of step D) to thereby obtain the desired compound of formula 1, such as 1-(4-thio-xcex2-D-arabinofuranosyl) cytosine.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description contained herein is to be regarded as illustrative in nature and not as restrictive.